Although various known clinical analyzers for chemical, immunochemical and biological testing of samples are available, clinical technology is rapidly changing due to increasing demands in the clinical laboratory to provide new levels of service. These new levels of service must be more cost effective to decrease the operating expenditures such as labor cost and the like, and must provide shorter turnaround time of test results to reduce the patient's length of stay in the hospital as well as improve efficiency of outpatient treatment. Modernization of analytical apparatus and procedure demands consolidation of work stations to meet the growing challenge placed on clinical laboratories.
Generally, analysis of a test sample involves the reaction of test samples with one or more reagents with respect to one or more analytes wherein it is frequently desired that the analysis be performed on a selective basis with respect to each test sample. However, due to the high demands placed on clinical laboratories regarding not only volume throughput but also the number and frequency of various analyses, there is a need to provide an automated analysis system which is capable of combining accurate analytical results, multiple test menu versatility, low reagent and fluids loss and consumption, and of great benefit and importance, continuous and high throughput.
The present automated clinical analysis systems provide much improved accuracy of analytical results in comparison with accuracies of earlier systems. In the present systems, analysis of a test sample typically involves forming a reaction mixture comprising the test sample and one or more reagents, and the reaction mixture is then analyzed by an apparatus for one or more characteristics of the test sample. Reliance on automated clinical analyzers has improved the efficiency of the laboratory procedures, inasmuch as the technician has fewer tasks to perform. Automated clinical analyzers provide results much more rapidly while frequently avoiding operator or technician error, thus placing emphasis on accuracy and repeatability of a variety of tests. Automated clinical analyzers presently available for routine laboratory tests include a transport or conveyor system designed to transport containers of sample liquids between various operating stations. For example, a reaction tube or cuvette containing a test sample may pass through a reagent filling station, mixing station, reaction forming station, detection stations, analysis stations, and the like. Such present transport systems are, however, not flexible in that transport is in one direction and the reaction tubes or cuvettes, once inserted into the apparatus, must pass through without access before analysis occurs. Even further, the present transport systems allow only batch-like operation in that once the system is initially loaded, testing may only be performed on the initially loaded samples during a single operation cycle; alternative or additional samples cannot be loaded during the operation cycle to allow continuing operations for extended periods. As for multiple test menu versatility, some of the presently available automated clinical analyzers, such as automated immunoassay analyzers like the Abbott IMx.RTM. analyzer and the Abbott TDx.RTM. analyzer (Abbott Laboratories, Abbott Park, Ill., U.S.A.), utilize procedures involving a variety of different assay steps. These present systems have typically relied on detection and measurement of optical changes in a reaction mixture during the assay process. For example, a number of well-known techniques using techniques using single or multi-wavelength fluorescence include fluorescent polarization immunoassays (FPIA) employing homogeneous immunoassay techniques, microparticle enzyme immunoassays (MEIA) employing heterogeneous immunoassay techniques, and the like. the MEIA technology, such as that used on the Abbott IMx.RTM. analyzer, is used for high and low molecular weight analytes requiring greater sensitivity, and FPIA technology, such as that used on the Abbott TDx.RTM. analyzer, is used primarily for lower molecular weight analytes. A front surface fluorometer is used in these systems to quantify a fluorescent product generated in the MEIA assays, while a fluorescence polarization optical system is used to quantify the degree of tracer binding to antibody in the FPIA assays. The test samples are automatically processed in certain of these systems, such as the Abbott IMx.RTM. analyzer and Abbott TDx.RTM. analyzer, by a robotic arm with a pipetting probe and a rotating carousel which positions the samples for processing. These systems are typically compact tabletop analyzers which offer fully automated, walk-away immunoassay testing capabilities for both routine and specialized immunoassays. These nonisotopic methods eliminate radioactivity disposal problems and increase reagent shelf life while meeting the diverse requirements of a multitude of different assays. Though these presently available automated clinical analyzers provide a degree of improved multiple test menu versatility in comparison to earlier systems and practices, the present analyzers remain limited in that these systems are one direction only systems, or batch analyzers, which permit the analysis of multiple samples and provide for access to the test samples for the formation of subsequent reaction mixtures, but permit only one type of analysis at a time. It would, thus, be an improvement to provide a random access analyzer which allows for analysis of multiple test samples for multiple analytes. It would be an even further improvement if such a random access analyzer allowed for continuous operations; that is, if additional or alternative samples could be loaded for analysis during analysis operations by the system, without interruption of the analysis operations. With respect to reagent and fluids consumption and loss in present automated clinical analyzers, a common feature of those analyzers is the inclusion of various reagents within the apparatus itself or placed near the apparatus for pipetting purposes. In these systems, liquid reagents, in bulk form, are selected for the various types of tests which are to be performed on the test sample, and are stored in or near the apparatus. Reagent delivery units, such as pumps and the like, along with valves, control and pipette mechanisms, are included in the present automated analyzers so that different reagents can be mixed according to the type of test to be performed. In certain of these present analyzers, for example, the Abbott IMx.RTM. analyzer previously mentioned, all the steps required for analysis of test samples are automatically performed and those steps include numerous checks of the subsystems to insure that assays are run to completion with valid results. In the Abbott IMx.RTM. in particular, quantification of the fluorescence intensity in the MEIA method and polarization in the FPIA method, as well as the final data reduction, are fully automated on the analyzer and results are printed by the analyzer and may be accessed through suitable means for automatic data collection by a laboratory computer. These various aspects of the present automated clinical analyzers, like the Abbott IMx.RTM., help limit reagent and fluid consumption and loss, as well as provide other advantages. Even with those advantages, however, improvement in reagent and fluids consumption and loss in an analysis system would be desirable. Even further, such improvement in consumption and loss by these, combined with benefits of continuous operations, accuracy of results, and test menu versatility would be a significant improvement in the art.
With respect to continuous and high throughput in automated analytical systems, the prior systems have been unable to provide these desirable characteristics. In the prior automated analytical systems, the systems are initially loaded with a plurality of test samples. The samples are then each tested during a full cycle of testing by the systems. Though the number of samples which may be initially loaded in these systems is fairly large, it is not possible to load additional test samples in these systems at the same time the systems are testing the initial load. Additional samples may only be loaded after testing of the prior sample load is complete. In order to increase throughput in these systems then, it would be advantageous to provide an automated analytical system which allowed for loading of additional samples at any time, even while the system is testing other samples. It would be an even further advantage if such a system could provide accurate results, multiple test menu versatility, and low reagent and fluids loss and consumption while at the same time allowing continuous access to and testing of samples. The prior systems have been unable to provide these advantages. The present automated continuous and random access system provides all these advantages. In addition to those advantages, the present invention also provides additional improvements directed to specific aspects, parts, and operations of these systems.
Other benefits and advantages, in addition to those previously described (i.e., accurate analytical results, multiple test menu versatility, low reagent and fluids consumption and loss, and continuous and high throughput), directed to specific aspects, parts, and operations of automated clinical analyzers would also be improvements in the art. For example, detecting the presence of liquid in a container is very important for the precise pipetting of test sample liquids, reagent liquids and buffer liquids stored in containers for use on such automated clinical analysis systems. Detecting the presence of the liquid or locating the surface thereof permits the controlled emersion of the pipette tip into the liquid. By controlling the depth of emersion of the pipette tip into the liquid, a consistent amount of liquid will adhere to the outside surface of the tip resulting in greater consistency of the total volume aspirated or dispensed. Non-invasive liquid surface sensing systems which are known include techniques such as utilizing a stepper motor for blowing or forcing air toward the surface of a liquid to detect the surface level of the liquid, as well as other electronic circuitry such as, for example, utilization of a bridged circuit for generating a signal corresponding to the vertical displacement of a pipette. However, problems exist with such liquid sensing systems. For example, blowing or forcing air against the surface of the liquid forms bubbles and generates aerosels in and around the liquid samples. With respect to electronic circuitry, for example, techniques using electrostatic capacitance between the pipette and the liquid are unstable because of variations caused by changes in humidity, parameter drift of the electronic devices with both time and temperature, and a decrease in the signal to noise ratio caused by the inability to provide suitable electrical grounding.